The top part of the filter casing is a calendar. The numbers indicate the months (01 –January, 02 – February, etc.) and the dots are the weeks of each month.
Whenever you start using a new filter cartridge, make sure to adjust the date on the calendar wheel to the day when the next cartridge change is due (i.e. today + 3 months).
The calendar is a handy visual reminder for when it is time to change the cartridge of your Flo Faucet Filter.